I know people have done the opposite and started @ LA and they returned to LA and then their final flight was say LA-Miami (they did that as a freebe) Now if a person can start out instead of finishing like that sorry I dont have any idea

What did they say when you called and asked them to do such a routing? you did call and ask didnt you for them to book it? if not why not, why ask on FT rather then ask UA worse come sto worse they will tell you you cant do it, then you wait a few mins and call back and try again, then and only then would I come onto FT and ask if anyone had any idea how I could do it